The present invention relates to a mobile communication system sharing of a frequency channel or a time slot and using a time division multiple access system (hereinafter referred to as TDMA) and/or a time division, code division multiple access system (hereinafter referred to as time divided CDMA), and in particular, it relates to a mobile communication system comprising a function in which a set of links, an up-link and a down-link, having different communication capacities from each other may be handled as a single communication channel (hereinafter referred to as an asymmetric communication channel).
A mobile communication system is mainly constituted with a mobile communication equipment or a portable communication equipment and a base station which communicates with mobile stations through radio channels. In such a mobile communication system, the common use of a radio frequency spectrum by different radio systems may be executed in a frequency division multiple access system (hereinafter referred to as an FDMA) or between a TDMA system and a CDMA system.
The common use of a frequency channel by different code systems has been put into an actual operation concerning the CDMA system.
A mobile communication system of a time slot common use type in which at least a TDMA signal and at least a time divided CDMA signal coexist in a time slot is disclosed in U.S. application Ser. No. 08/524,974 which is separately applied by the same applicant as the present invention, however, an asymmetrical communication channel is not all at referred to in the application.
Technologies for mobile communication systems in which a time slot is commonly used and a frequency channel is also commonly used, and further, technologies for synchronizing radio base stations by a wireless local loop (hereinafter referred to as WLL) using semi-fixed communication equipment are known in the art. However, in these technologies, an asymmetric channel in which capacities of an up-link and a down-link are different is not known.
The U.S. Pat. No. 5,363,403 is known as a system in which a plurality of CDMA signals are commonly used. However, in the specification, nothing is described concerning the way of handling a time divided CDMA. The U.S. Pat. No. 5,511,068 is also known as another mobile communication system, however, it is related to an adaptive filter in a time divided CDMA system and in the specification nothing is nothing refers to the common use of a frequency channel of a CDMA signal and a TDMA signal in a single time slot.
As a communication system in which a TDMA technology is applied to a CDMA communication system, the U.S. Pat. No. 5,410,568 is known. In the patent, a synchronization code is placed at the head of a burst signal. The patent does not refer to a system in which a time divided CDMA system is introduced using a TMDA control channel for setting frame synchronization, and nothing refers to coexistence with a TDMA system. In other words, it is not a patent in which TDMA system and a time divided CDMA system are to be used in common using a TDMA frame. Further, no consideration is paid for an asymmetrical channel in which the capacity of an up-channel is different from that of a downchannel.
Besides the above-mentioned ones, JP-A-63/175526, JP-A63/175527, JP-A-5/145477, JP-A-7/154866, and JP-A-8/186533, and so on are known.
However, in the above-mentioned JP-A-63/175526 and JP-A63/175527, it is intended to send more signals under the condition that the transmitting power of a transponder in a satellite communication is limited, but in the case of a mobile communication on land, such a limitation does not exist. Furthermore nothing describes a time divided CDMA system or a high speed TDMA. JP-A-5/145477 is related to the control of transmitting power of a signal in a TDMA time slot, and nothing refers to the time divided CDMA and TDMA communication systems.
The above-mentioned JP-A-7/154866 and JP-A-8/186533 are applications in which a set of links, an up-link and a down-link of having different capacities from each other may be handled as a communication channel. In the former, however, there is no concrete description about a high speed TDMA data transmission or a low speed time-divided CDMA data/voice frequency signal transmission, and nothing refers to a control information channel for intermittent connection which connects a user and a database during the consideration of the user or to the increase or decrease of a guard time in the unit of a micro time slot in a high speed TDMA data transmission channel. In the latter, as understood from the explanation of an aloha with a slot, it is premised on a packet communication system, and the time ratio of an up-link to a down-link in a time division duplex communication system can be variable, but it does not vary the time ratio of the up-link to down-link in a TDMA-TDD frame. Therefore, nothing refers to the coexistence of a plurality of TDMA signals, high speed TDMA data transmission and time divided CDMA in a time slot.
As mentioned in the above, there are many kinds of systems being constituted of one or more base stations which communicate with a plurality of mobile stations through radio channels using a TDMA system and a time divided CDMA system have been known. In these mobile communication systems, there has been a demand to introduce a high speed data communication system, however, a mobile communication system which is able to correspond such a demand has not been realized.
In order to make a mobile communication system to be able to correspond to a multimedia communication, it is needed to introduce a communication channel in which the communication capacity in an up-link and that in a down-link are different.
The present invention was made to solve the problems as mentioned in the above, and the object of the present invention is to realize a mobile communication system which is able to correspond to a multimedia environment, wherein a high speed TDMA channel is introduced to a mobile communication system in which a TDMA signal and a time divided CDMA signal coexist, and furthermore, communication links having different communication capacities in an up-link and a down-link may be handled as a single communication channel.
A mobile communication system described in claim 1 according to the present invention is the one in which a high speed data channel is introduced and the communication channel is made to be an asymmetric one in which the communication capacity of the up-link and that of the down-link are different from each other. Thereby, it is made possible to change over the communication speed in the unit of a frame length, which has been needed by customers, and to realize a mobile communication system which is able to flexibly adapt to the variation in communication capacity, which has been required by the multimedia environment.
A mobile communication system described in claim 2 according to the present invention is one in which the ratio of the communication capacity of an up-link to that of a down-link is varied by shifting a frame time, a TDD line in a frequency axis, in the direction of the time axis.
A mobile communication system described in claim 3 according to the present invention is the one comprising an asymmetric communication channel in which the down-link is assigned a high speed TDMA data channel and the up-link is assigned a low speed TDMA data channel.
A mobile communication system described in claim 4 according to the present invention is an asymmetric communication system in which the down-link is assigned a high speed TDMA data channel and the up-link is assigned a low speed time divided CDMA data channel.
A mobile communication system described in claim 5 according to the present invention is an asymmetric communication system in which the down-link is assigned a low speed TDMA data channel and the up-link is assigned a high speed TDMA data channel.
A mobile communication system described in claim 6 according to the present invention is an asymmetric communication system in which the down-link is assigned a low speed time divided CDMA data channel and the up-link is assigned a high speed TDMA data channel.
A mobile communication system described in claim 7 according to the present invention comprises at least a TDMA burst signal and at least a time divided CDMA burst signal, with both of them or either of them being used as a control channel.
A mobile communication system described in claim 8 according to the present invention is provided with a mobile switching center for the management of an asymmetric channel, and the switching center is so designed to be able to instruct at least one base station to change the information quantity in an up-link and a down-link.
A mobile communication system described in claim 9 according to the present invention comprises an asymmetric communication channel, and as soon as the transmission of a large information quantity of data is finished, the data channel for the transmission of a large quantity of data is switched to a data channel for the transmission of a small quantity of data. Thereby, the situation is avoided in which a communication channel for the transmission of a large quantity of data is needlessly occupied while data are not actually transmitted.
A mobile communication system described in claim 10 according to the present invention in which when a base station is connected to a mobile station with a channel for small quantity of data, if there is no transmission of data through the channel for a predetermined period of time, the channel is switched to a control channel for connection.
A mobile communication system described in claim 11 according to the present invention in which when a base station is connected to a mobile station with a control channel for connection, if there occurs a demand for the transmission of a large quantity of information data, the channel may be immediately switched to a transmission channel for a large quantity of data.
A mobile communication system described in claim 12 according to the present invention in which when a base station and a mobile station are connected to each other with a control channel for connection, if there occurs a demand for the transmission of a small quantity of information data, the channel may be immediately switched to a transmission channel for a small quantity of data.
A mobile communication system described in claim 13 according to the present invention in which a base station and a mobile station are connected to each other with a channel for a small quantity of data, if there occurs a demand for the transmission of a large quantity of information data, the channel may be immediately switched to a channel for the transmission of a large quantity of data.
A mobile communication system described in claim 14 according to the present invention in which a mobile switching center is provided to perform the management of an asymmetric channel, and the mobile switching center is able to instruct at least one base station in the switching of an asymmetric channel.
A mobile communication system described in claim 15 according to the present invention comprises an asymmetric channel and further the down-link and the up-link utilizing multi-frames are respectively provided with independent transmission channels for a small quantity of data. During a period of time being used by a user, a period of time for his consideration after his receipt of a lot of information for example, the influence caused by hardware upon the depth or length of the user""s consideration is avoided by using a transmission channel for a small quantity of data as a control circuit for intermittent connection to connect the user and a database offerer with minimum control data.
A mobile communication system described in claim 16 according to the present invention in which control data are transmitted using a data channel for a small quantity as a control information channel for an intermittent connection while data are not exchanged between a base station and a mobile station.
A mobile communication system described in claim 17 according to the present invention in which during the period of time till an answer is issued from a mobile station after a large quantity of data is received by the mobile station, control data showing that there is no data being exchanged between the base station and the mobile station are also transmitted in the control information channel for the intermittent connection.
A mobile communication system described in claim 18 according to the present invention in which a mobile switching center is provided for the management of a control information channel, and the mobile switching center is able to instruct at least one base station in starting, switching and discontinuation of the control information channel for intermittent connection.
A mobile communication system described in claim 19 according to the present invention comprises an asymmetric channel, and furthermore, a time slot of a high speed TDMA data channel is constituted with a plurality of micro time slot elements connected in series. Thereby, except the difference in speed, a low speed data processing unit and a high speed data processing unit may be the same constitution, and the constitution of the whole system is simplified and the costs of equipment and design may be decreased. Furthermore, it is made possible to increase or decrease the guard time in the unit of a micro time slot, so that a proper guard time may be set corresponding to the speed of a moving body, which means that interference by another time slot may be avoided and at the same time lowered efficiency may be prevented.
A mobile communication system described in claim 20 according to the present invention in which a micro time slot in a high speed TDMA data channel is formed with the same bit constitution as that of a time slot in a low speed TDMA data channel.
A mobile communication system described in claim 21 according to the present invention in which an equalizer for a high speed TDMA data channel is made to have the same constitution as that for a low speed TDMA data channel except the difference in operating speed.
A mobile communication system described in claim 22 according to the present invention in which the guard time in a high speed TDMA data channel may be varied in the unit of a micro time slot corresponding to the moving speed of a mobile station.
A mobile communication system described in claim 23 according to the present invention is provided with a mobile switching center for the management of the constitution of a micro time slot in a high speed TDMA data channel and the mobile switching center is arranged to be able to instruct at least one base station in the change concerning the constitution including the guard time length of the high speed TDMA data channel.
A mobile communication system described in claim 24 according to the present invention comprises an asymmetric channel, and further switches for selecting a communication system which is able to transmit a necessary information quantity in synchronization with time slots are provided in at least one base station and a plurality of mobile stations. Thereby an asymmetric channel may be realized by assigning channels having different communication systems to each other to a down-link and an up-link in TDD time slots, and it is possible to realize both asymmetry in transmission communication capacity and asymmetry in time.
A mobile communication system described in claim 25 according to the present invention in which a memory is provided to at least one base station, the memory which makes it possible to assign a channel to a down-link and another channel to an up-link independently of each other concerning a single mobile station.
A mobile communication system described in claim 26 according to the present invention is provided with a mobile switching center for the management of the assignment of communication channels, and the mobile switching center is arranged to be able to instruct at least one base station in the assignment of channels.
A mobile communication system described in claim 27 according to the present invention comprises an asymmetric channel, and a mobile switching center is provided with a memory for registering the information of mobile stations managed by the mobile switching center. Thereby, the services to be given to the mobile stations being managed by the mobile switching center may be easily known and the channel assignment may be effectively performed.
A mobile communication system described in claim 28 according to the present invention in which a mobile switching center manages mobile station information concerning the mobile stations being managed by the mobile switching center, and the mobile switching center is able to instruct at least one base station in the starting, switching and discontinuity of services based on the mobile station information.
A mobile communication system described in claim 29 according to the present invention in which a mobile switching center manages the information concerning mobile stations being managed by the mobile exchange, and when a revision in a mobile station information occurs, and the revised information is transferred to the database of the mobile communication system which stores mobile station information in the whole mobile communication system, through at least one public switching telephone network.
A mobile communication system described in claim 30 according to the present invention comprises an asymmetric channel, and a memory device for high speed data communication which temporarily stores high speed data to be transmitted to a mobile unit is provided in a mobile switching center. Thereby, it is made possible to correspond promptly to a request for high speed data transmission from a user, and also a partial loss of high speed data may be prevented.
A mobile communication system described in claim 31 according to the present invention in which when the transmitted high speed data are normally received in a mobile station, a normal time slot number when the end of the high speed data are received is detected in the mobile station and the number is reported to a mobile switching center.
A mobile communication system described in claim 32 according to the present invention in which a mobile switching center manages high speed data transmitted to a mobile station, and the switching center is provided with a function to store high speed data having time slot numbers on and after the number next to the normal slot number transmitted from the mobile station in a memory device to be used for the high speed data communication.
A mobile communication system described in claim 33 according to the present invention in which a mobile switching center performs the management of high speed data to be transmitted to a mobile station, and the switching center is provided with a function as described below: when there is a request from the mobile station to transmit the high speed data again, it reads the high speed data having the time slot number on and after the number next to the normal time slot number out of the memory device to be used for high speed data communication and transmits the high-speed data to the mobile station.
A mobile communication system described in claim 34 according to the present invention in which a mobile switching center is provided with a function as described below: when the high speed data to be transmitted to a mobile station are stored in a memory device to be used for a high speed communication, the mobile switching center divides the high speed data received from the originating end of the high speed data through a public switching telephone network into blocks of information so that each of the blocks is composed of an information quantity which may be transmitted in a time slot and manages the blocks in numbering each block with a storing information number.
A mobile communication system described in claim 35 according to the present invention in which a base station is provided with a function to compare the time slot number of high speed data transmitted to a mobile station with the storage information number marked by the mobile switching center and to combine the information consisting of the time slot number and the storage information number into a set of information and transmit the information the information to the mobile switching center.
A mobile communication system described in claim 36 according to the present invention in which a mobile switching center performs the management of high speed data to be transmitted to a mobile unit, and also it is given a function to erase high speed data having slot numbers previous to the normal time slot number transmitted from the mobile station from the memory device for high speed data communication.
A mobile communication system described in claim 37 according to the present invention in which a mobile switching center performs the management of high speed data to be transmitted to mobile stations and also it is given a function to inform an originating end of the high speed data regarding the information quantity of high speed data having time slot numbers on and after the normal slot number which are left in the memory device for high speed communication to when a mobile unit finishes communication.
A mobile communication system described in claim 38 according to the present invention in which a mobile switching center performs the management of high speed data to be transmitted to mobile units and also it is given a function to request the forwarding of succeeding high speed data to an originating end of the high speed data if the quantity of data left in the memory device for a high speed communication decreases lower than a predetermined level during the transmission of high speed data requested by a mobile station to a base station.
A mobile communication system described in claim 39 according to the present invention in which when transmitted high speed data are not normally received in a mobile station, the mobile station is given a function to detect the slot number of the high speed data and to transfer the slot number as an abnormal slot number to a mobile switching center.
A mobile communication system described in claim 40 according to the present invention in which a mobile switching center performs the management of high speed data to be transmitted to mobile stations and also the switching center is given a function as shown below: when the mobile switching center receives an abnormal time slot number sent from a mobile station, it reads the high speed data having the abnormal time slot number out of a memory device for a high speed data communication and transmit the data again to the mobile station.
A mobile communication system described in claim 41 according to the present invention comprises an asymmetric channel and in which a mobile switching center is provided with a mobile station management memory for storing a communication channel management list for managing communication channels of respective mobile units, and the mobile switching center assigns a time slot corresponding to a transmission type and after the operation assigned to the time slot corresponding to the present transmission type is over, the time slot assignment is kept in the mobile station management memory as history of data, and when the same transmission type is assigned again, the time slot number kept in the memory is used again. Thereby, the up-link and the down-link may be set independently of each other with different types of transmission.
A mobile communication system described in claim 42 according to the present invention in which in a case where the existence of a time slot name of the same transmission type which has the history of actual use in the mobile station management memory is gone, the history of actual use of the slot name in the past is erased from the mobile station management memory, and the time slot is arranged to be assigned for the use of a new mobile station.
A mobile communication system described in claim 43 according to the present invention in which when the history of a time slot which has the history of actual use in the past is going to be erased, a time slot which has the oldest history of actual use is selected and it is arranged to be assigned as a time slot for a new mobile station.